Ion implantation is a standard technique for introducing conductivity-altering impurities into a workpiece. A desired impurity material is ionized in an ion source, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the workpiece. The energetic ions in the beam penetrate into the bulk of the workpiece material and are embedded into the lattice of the workpiece material to form an implanted region.
Workpieces or films on workpieces may be composed of many different materials. For example, ZnTe is a wide band gap semiconductor material with a direct band gap of around 2.25 eV. ZnTe may be used in ultra-high efficiency solar cells, pure green light emitting diodes (LEDs), laser diodes, optoelectronic detectors, compound semiconductors, and other applications known to those skilled in the art. However, it is difficult to perform n-type doping of ZnTe or ZnTe workpieces. In-situ doping during ZnTe growth has been performed, such as using molecular beam epitaxy (MBE) or metalorganic chemical vapor deposition (MOCVD). Doping during ZnTe growth cannot control the Zn vacancy concentration, which is one mechanism that prevents n-type doping of ZnTe. This is at least partly because in-situ doping during ZnTe growth involves competition between dopants and Zn atoms. This competition results in Zn vacancies. The existence of Zn vacancies is a p-type characteristic and will compensate for n-type doping of ZnTe. What is needed is a new method of doping ZnTe and, more particularly, n-type doping of ZnTe.